Manchester United's 2-0 defeat to Chelsea on Saturday left Michael Carrick's side 17th in the Premier League table, with just seven points from their opening nine matches. The result extended a miserable run and left them narrowly outside the relegation zone.
Ten Hag, now technical director at FC Twente, believes the club cannot dismiss the possibility of dropping into the Championship given the strength of the division.
“In the Premier League it's certainly possible, because all the teams are simply strong. They're all strong squads, all good managers,” he told ESPN Netherlands.
“And if you end up on the wrong side once and you really get into that vicious circle – yes, then it can become very, very difficult.”
United avoided falling into the bottom three over the weekend because Crystal Palace, Nottingham Forest and Sunderland also failed to win. However, their poor away record is another concern: they have failed to win any of their first seven away matches in all competitions for the first time since the 1973-74 season, when they were relegated.
Ten Hag also reflected positively on his own time at Old Trafford, despite the difficult final period of his tenure.
“I think we performed pretty well with United. I think we had performed more than pretty well. We couldn't have done it better,” he said.
“Before we arrived, six years without winning a trophy. Look where they are now. We were at Wembley six times, we played two FA Cup finals. We won two trophies, we finished third.”
The Dutchman also returned to his strained relationship with Ronaldo, who left United in November 2022 after a public dispute with the manager and the club's hierarchy.
In a separate interview with ESPN, Ten Hag argued that the Portuguese forward had not been able to maintain the standards required at the highest level since leaving Real Madrid for Juventus in 2018.
“Every top team must embrace the top player, but the top player must also make way for the team. That was simply the problem with Ronaldo,” he said.
“He is of course a tremendous player, one of the greats of all time. But that is also the reality over the last seven, eight years: he simply can no longer deliver. From Juventus onwards it's simply over.”
Ten Hag said Ronaldo had struggled to meet the physical demands of the Premier League and questioned whether he was still prepared to push himself through pain and train at maximum intensity.
The former United manager also praised Real Madrid for recognising when it was time to part ways with an ageing star, arguing that the Spanish club had moved Ronaldo on while his reputation remained high.
His comments come at a difficult moment for United, with Carrick under pressure to turn around the team's form. Ten Hag's warning about a downward spiral is particularly pointed given the club's current position, while his latest remarks about Ronaldo reopen one of the most divisive chapters of his Old Trafford reign.